    Patent Literature 1: JP 3725693 B1    Patent Literature 2: WO 2007/024894 A
Various types of techniques for detecting water leakage in water pipes have been proposed. In recent years, waterworks as infrastructure are getting older on a nationwide basis. Therefore, in view of prevention of unnecessary water consumption and damage to buildings, it may be preferable to detect water leakage at a minute level and take measures promptly.